1. Field of the Invention
The present invention relates to novel compounds which are useful as metal corrosion inhibitors. The compounds are N-aryl or N-alkyl substituted pyridinium halides wherein the pyridinium ring itself is further connected to one or more heteroatoms containing alkyl or aryl groups.
2. Description of Related Art
It is known that at high operating temperatures halide ions, such as chloride and bromide ions, are extremely aggressive toward corrosion of many containment materials such as steel, stainless steel, and copper. The type of corrosion exhibited by these metals in strong salty aqueous environments containing oxygen is pitting. Pitting corrosion is one of the most severe types of corrosion. As an example, a single pit penetrating through the containment material in a pressurized system can put the entire system out of action until the damage is repaired. Thus, precautions must be taken beforehand to prevent such failures, which involve direct repair costs as well as downtime costs.
Three basic methods can be used to combat corrosion problems of this nature. These are:
(a) choose a more corrosion-resistant material (which in many cases is economically unattractive);
(b) use a corrosion-resistant coating (which is likely to fail with many commonly used inexpensive coating materials becuase of the temperture cycling involved); and
(c) use adsorption type synergistic corrosion inhibitors stable up to 230.degree. C. or higher.
Among these, the use of adsorption-type synergistic corrosion inhibitors appear to be an attractive approach in terms of both effectiveness and cost.
Some general references in this art include:
G. Schmitt, et al., in Werkstoffe und Korrosion, Vol. 36, pp. 273-278 published in 1985 disclose some studies relating to structural and electronic effects in acid inhibitors by AC impedance measurements. The acid inhibitors include N-benzyl quinoline derivatives and N-substituted pyridine derivatives. This reference does not teach or suggest the alkylamine-ring substituted pyridines having N-substituted methylnaphthalenes.
D. R. Napier et al. in U.S. Pat. No. 3,288,555 disclose a method of inhibiting corrosion. The inhibitors are prepared by reacting a halomethylated alkyl aromatic compound with a double bonded, conjugated nitrogen compound.
R. P. Annand et al. disclose in U.S. Pat. No. 3,982,894 a method of inhibiting acidic corrosion of ferrous metals with polyquaternary amino polymers.
L. Helb, et al. disclose in U.S. Pat. No. 3,974,220 the use of polymeric quaternary ammonium corrosion inhibitors and petroleum demulsifiers in crude oil refining.
R. G. Asperger et al. in U.S. Pat. No. 4,100,099 disclose quaternary salt-polyamine inhibitors for sour gas conditioning solution used to remove CO.sub.2 and H.sub.2 S from a gas stream where corrosion is effectively inhibited by a combination of a quaternary pyridinium salt and a lower alkylenepolyamine or corresponding polyalkylenepolyamine.
M. Patsch, et al., in U.S. Pat. No. 4,212,709 disclose an acidic nickel electroplating bath containing sulfobetaines as brighteners or leveling agents. The leveling agents have the formula: ##STR2## Where only for the purpose of describing these agents in this paragraph, ##STR3## is a heteroaromatic nitrogen base, R, R.sup.1 and R.sup.2 are hydrogen or aklyl, R.sup.3 is arylene, X is SO.sub.3 -, Y is a neutralizing cation, n is from 1 to 3, and m is from 1 to 2.5.
P. M. Quinlan in U.S. Pat. No. 4,071,746 discloses alkylbenzyl pyridinum compounds of the general formula: ##STR4## where only for the purposes of describing these agents in this paragraph, R is a hydrocarbon group, occurring n times in the ring and R' is a hydrocarbon group occurring m times and X.sup.- is an anion, preferably halogen. These compositions are employed as corrosion inhibitors preferably in acid systems. They are preferably employed as corrosion inhibitors with surfactants and preferably with surfactants and alcohols.
T. E. Fisk, et al. in U.S. Pat. No. 4,672,118 disclose corrosion inhibitors for metal surfaces in contact with an aqueous medium by incorporating an N-(hydrophobearomatic) pyridinium compound such as N-(p-dodecylphenyl)-2,4,6-trimethyl pyridinium sulfoacetate into the aqueous medium.
Additional references of interest include:
R. Vilceanu, et al., Rev. Chim. (Bucharest), Vol. 32, p. 327 (1981).
S. Hettiarachchi et al., Proc. 15th International Seminar in Chemical Engineering and Physical Chemistry, University of Karlsruhe, West Germany, July (1980).
S. Hettiarachchi, et al., NACE CORROSION '87, Presentation, March (1987).
S. Narang, et al., J. Polym. Sci. Polym. Lett. Ed., Vol. 23, p. 147 (1985).
All of the above references are incorporated herein by reference. None of these references individually or collectively teach or suggest the present invention. It is therefore desirable to have useful synergistic corrosion inhibitors of the structures described herein.